Wednesday evening, a mother came home to her West Point, Utah home and found her 4-year-old son dead. She called 911, and police discovered her 10-year-old son found dead in a lower part of the home. Police believe their 15-year-old brother murdered both of them. Both of the younger boys appeared to have been stabbed to death. Though a jury may have to ultimately decide the case, the boy allegedly killed his adopted brothers.

“As a result of our investigation, this morning we have taken the 15-year-old juvenile into custody,” Sergeant Susan Poulsen said, adding that prosecutors were expected to formally charge the boy on Monday. “We believe he acted alone.”

The older boy was home alone babysitting his younger brothers. His mother was out, and his father is in the military in Alabama. The fifteen year old is a natural born child, and the ten and four year olds had been adopted.

At first, police were uncertain as to the fate of the older boy who was missing. Around midnight they found him walking down a road. He had multiple blood stains, but no weapon. Two weapons were later found in the home after a search by the forensic team.

Sheriff Todd Richardson said he will be facing two homicide charges. He told CNN: “He had been interviewed by one of our detectives, and there has been things that have been brought forth that is part of an active investigation, and as time goes on, it will be released as to why he did what he did.”

“I don’t want to speculate what was going through his mind, but he is a natural child of the family and the two children who were victims in this were both adopted,” the sheriff added.

The fifteen year old boy had run away from home once before, and was returned by the sheriff’s department. The family received assistance from a church member who performed an ‘intervention’ with the family. Authorities are not aware if the boy received any other psychological care.

“We believe the suspect acted alone, and no other suspects are at large,” the sheriff’s office said in a statement.

This tragic event follows the stabbing of an eight year old girl by her twelve year old brother on April 27th in northern California.

The first reports said that an intruder had entered the home. The twelve year old boy was in the bathroom. The eight year old girl began screaming, and the alleged intruder ran out of the home.

Police searched the area for days, and finally arrested the boy four days later.

The boy was calm when interviewed by police with his attorney present. He is charged with second degree murder.

The boy is the natural child of the mother, and the slain girl was his step sister.